Emergence of thermodynamic functioning regimes from finite coupling between a quantum thermal machine and a load

TL;DR

This paper investigates how finite coupling in quantum thermal machines influences their operational regimes, revealing mode transitions and quantum effects that affect thermodynamic functioning.

Contribution

It introduces a detailed analysis of mode switching in quantum thermal machines based on coupling strength and temperature tuning, highlighting quantum effects like bosonic enhancement.

Findings

Increasing coupling suppresses engine mode

Refrigerator mode becomes unattainable at strong coupling

Quantum effects amplify regime switching

Abstract

Autonomous quantum thermal machines are particularly suited to understand how correlations between thermal baths, a load, and a thermal machine affect the overall thermodynamic functioning of the setup. Here, we show that by tuning the operating temperatures and the magnitude of the coupling between machine and load, the thermal machine can operate in four modes: engine, accelerator, heater, or refrigerator. In particular, we show that as we increase the coupling strength, the engine mode is suppressed, and the refrigerator mode is no longer attainable, leaving the heater as the most pronounced functioning modality, followed by the accelerator. This regime switching can be amplified by quantum effects, such as the bosonic enhancement factor for a harmonic oscillator load, which modifies the effective machine-load coupling, making the thermodynamic functioning sensitive to the initial preparation of the load.